Biomedical wireless sensors require thin, lightweight, and flexible single-layer structures operating in immediate proximity of human body. This poses a challenge for RF and antenna design required for wireless operation. In this work, the radio interface design for a 2.4 GHz wireless sensor including a discrete filter balun circuit and an antenna operating at 0.3 mm distance from the body is presented. Thin, lightweight single-layer structure is realized using printed electronics manufacturing technology. The RF and antenna designs are validated by measurements, and a sensor with a fully functional radio interface is implemented and verified. At 0.3 mm from the body, 2.4 dB insertion loss and -10 dBi realized gain at 2.4 GHz were achieved for a discrete lter balun and antenna, respectively. The received power level on a Bluetooth low energy (BLE) channel was above -80 dBm at 1 m distance from the body, indicating capability for short-range off-body communications. The paper also provides guidelines for printed electronics RF and antenna design for on-body operation.
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